The invention relates generally to monitoring and controlling temperature and, more specifically, a method and apparatus for monitoring and controlling food temperature.
Produced food travels from processing plants to grocery stores, where the food product remains on display case shelves for extended periods of time. For improved food quality, the food product should not exceed critical temperature limits while being displayed in the grocery store display cases. For uncooked food products, the product temperature should not exceed 41xc2x0 F. For cooked food products, the product temperature should not be less than 140xc2x0 F. In other words, the critical temperature limits are approximately 41xc2x0 and 140xc2x0 F. Between these critical temperature limits, bacteria grow at a faster rate.
One attempt to maintain food product temperature within safe limits is to monitor the discharge air temperature to ensure that the display case does not become too warm or too cold. But the food product temperature and discharge air temperature do not necessarily correlate; that is, discharge air temperature and food product temperature will not necessarily have the same temperature trend because food product temperatures can vary significantly from discharge air temperature due to the thermal mass of the food product. Further, during initial startup and display case defrost, the air temperature can be as high as 70xc2x0 F. while food product temperature is much lower for this typically short interval. Finally, it is impractical to measure the temperature of food products at regular intervals in order to monitor food product temperature in a display case.
More specifically, in a conventional refrigeration system, a main controller typically logs or controls temperature. Conventionally, the main controller is installed in the compressor room, which is located on the roof or back of the grocery store. The conventional method for monitoring and controlling the display case temperature requires a discharge air temperature sensor mounted in the display case. The discharge air temperature sensor is typically connected to an analog input board, which is also typically located in the compressor room. A temperature wire must be pulled from the display case to the compressor room, which is typically difficult and increasingly expensive depending on how far away the compressor room is from the display case. Further, this wiring and installation process is more expensive and extremely cumbersome when retrofitting a store.
An apparatus, system, and method for controlling a refrigeration system according to the invention overcomes the limitations of the prior art by providing wireless transmission of simulated product temperature data. An apparatus according to the invention includes a plurality of circuits having at least one refrigeration case and a compressor rack. An electronic evaporator pressure regulator in communication with each circuit controls the temperature of one of the circuits. A sensor in communication with each circuit measures a parameter from the circuit, and a transceiver in communication with the sensor wirelessly transmits the measured parameter. A receiver receives the wirelessly transmitted measured parameter. A controller in communication with the receiver controls each electronic evaporator pressure regulator and a suction pressure of said compressor rack based upon the wirelessly transmitted measured parameter from each of the circuits.
Preferably, at least one of the sensors in communication with each of the circuits is a product-simulating probe operable to simulate a product temperature. The probe for simulating product temperature includes a housing containing a thermal mass having thermo-physical properties similar to food product, and a temperature sensing element for measuring the temperature of the thermal mass. Preferably, the thermal mass is contained within a plastic bag within the housing. The transceiver, which is connected to the temperature-sensing element, wirelessly transmits the measured temperature data to the receiver. The transceiver may be disposed within the housing, or positioned external to the housing. The housing preferably includes a middle plate supporting the thermal mass in a first portion of the housing and containing the temperature sensing element in a second portion of said housing. Most preferably, the middle plate includes a channel communicating with the second portion and extending into the first portion, and the temperature-sensing element is positioned within the channel such that the thermal mass substantially surrounds the channel.